Patent
1983-01-05
1984-12-25
Adams, Russell E.
G03B 3900
Patent
active
044900287
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an exposure-control device on an aerial camera with an arrangement at whose input ends there are signals of the measured values for the flying speed v and the flying height h or the quotient v/h and for the permissible image motion .DELTA.s.sub.perm for determining the maximum permissible exposure time T.sub.perm in accordance with the formula ##EQU1## and for the exposure interval (cycling time), with an exposure meter for the continuous integral metering of the brightness of the terrain being overflown, with devices to control diaphragm and shutter.
In a device which has become known, a signal is emitted by an exposure meter directed upon the terrain to be photographed, which sets the shortest possible shutter time and the aperture to the corresponding value. As the brightness decreases the diaphragm is opened wider in accordance with the light conditions encountered, up to its maximum aperture. If the light decreases even further, the shutter time is also altered to longer time values (Manual of colour aerial photography 1968, p144).
In another device which has become known, for the automatic control of exposure, the terrain to be photographed is scanned by an exposure meter and the corresponding signals are fed to an operational amplifier which generates an output signal which is used to control the exposure of the photograph.
In this, an exposure-control device is connected with a v/h sensor, whose signals directly influence the exposure control accordingly and which in addition also control the exposure sequence (Manual of Photogrammetry 1966, 3rd edition, p172). In yet another exposure-control device v/h value is also used, together with other photographic values, such as filter factor, permissible image motion, etc. in order to obtain and set the maximum permissible exposure time dependent on the v/h value. In a second computer the corresponding aperture is computed and set for this time setting, in accordance with the brightness conditions measured with an exposure meter. In addition, a further control device can react upon the arrangement to control exposure time in the limiting ranges of the (maximum and minimum) aperture settings (DE-PS No. 24 03 862).
In these instruments the disadvantage resides in the fact that the exposure-control device is essentially based on a time value which is either preset and fixed or which depends on v/h and in which the diaphragm is adjusted according to the lighting conditions encountered.
Thus, the lens aperture with the optimum imaging performance is not generally available for the exposure.
However, it is desirable to utilize the optimum imaging quality of the lens system used, and this lies within the optimum aperture range.
It is one of the objects of the present invention to create an exposure-control device for an aerial camera which avoids these disadvantages and which regulates aperture and exposure time by optimizing criteria which take into account the substantially continuously measured brightness of the terrain being overflown and to be photographed, the lens aperture producing the substantially optimum imaging performance, the dynamic control characteristics of the devices controlling diaphragm and shutter, and the permissible or tolerable image motion, in order always to work within the optimum exposure range even when the terrain conditions are variable both as regards the terrain itself and also with regard to the lighting conditions encountered. Despite this, the exposure-control device should be of simple construction and provide the operator with the possibility of manual intervention for correction or permit automatic correction when the brightness conditions occur that would falsify the picture content. Moreover, it is desirable for the exposure-control device to have a self-monitoring device, in order to enable the operator to recognize and possibly correct any functional defects during the survey flight itself.
The objective can be achieved if, in accordance with the present invention, an exposure-control circuit d
REFERENCES:
patent: 3163098 (1964-12-01), Kierstead,Jr.
patent: 3324777 (1967-06-01), Kanner
patent: 3469515 (1969-09-01), Hillman
patent: 3608453 (1971-09-01), Dirksen et al.
patent: 3997795 (1976-12-01), Pohl et al.
Adams Russell E.
Wild Heerbrugg Aktiengesellschaft
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